The present invention relates to end closures for two-piece beer and beverage metal containers having a non-detachable operating panel. More specifically, the present invention relates to forming techniques for improving the openability of a lightweight end closure.
Common end closures for beer and beverage containers have a central panel that has a frangible panel (sometimes called a xe2x80x9ctear panel,xe2x80x9d xe2x80x9copening panel,xe2x80x9d or xe2x80x9cpour panelxe2x80x9d) defined by a score formed on the outer surface, the xe2x80x9cconsumer side,xe2x80x9d of the end closure. Popular xe2x80x9cecologyxe2x80x9d can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the remainder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a xe2x80x9cstay-on-tabxe2x80x9d (xe2x80x9cSOTxe2x80x9d) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cut-edge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
These containers are typically filled with carbonated beverages that create a substantial pressure within the container. Upon opening the container, this pressure must be quickly and safely vented. For this reason can ends are constructed for venting or releasing the internal pressure of the container during the initial opening of the container.
When the tab is lifted, an upward force is placed on a rivet that attaches the tab to the end, and a downward force is placed on the tear panel. This causes an initial opening of the tear panel beneath the nose of the tab in an area referred to as the vent region of the can end. Further lifting of the tab causes the tear panel to separate progressively along the score.
Upon fracturing of the vent region, rapid disassociation of the tear panel from the end panel, or more simply, the xe2x80x9cmissilingxe2x80x9d of the tear panel may occur. For this reason, some manufacturers place anti-missile features on the consumer side of the can end.
One such feature consists of a vent coin inside the score line. This feature causes localized compression. This score compression causes the edge of the tear panel to move over the end panel as illustrated in FIG. 4 of the drawings. Thus, the anti-missile feature and score help prevent the rapid disassociation of the tear panel from the end panel when the end is opened under the pressure provided by the carbonated beverage in the can.
It is an object of the present invention to provide an end closure for a container having an improved openability and resistance to missiling. The end closure includes a vent coin. The vent coin is a substantially obround shaped coin located adjacent to a score groove. The vent coin displaces metal of a large enough area to cold work a residual metal between the score groove and a product side of the end closure. This causes an elastic, compressive state.
The vent coin of the present invention collapses the score groove. This is accomplished by moving the vent coin outside of a tear panel defined by the score groove and on the public side of the end closure. A similar result is reached when the vent coin is provided on the tear panel but on the product side of the end closure rather than the public side.
The tear panel is slightly tucked below the adjacent portion of the end closure. A first plane of metal defined by the tear panel underlaps a second plane of metal defined by the region of the end closure on the opposite side if the score groove as the tear panel. This is accomplished by placing the vent coin in a location where the residual metal between the score groove and the product side is cold worked such that a flow of plastically deformed residual metal is forced inwardly and over the tear panel.